Water softening equipment is typically NOT installed on lines supplying which of the following?

Water softening equipment is generally not installed on lines supplying lawn irrigation systems primarily because the addition of softened water can lead to ecological impacts and might not be necessary for irrigation purposes. Softened water, which typically contains higher sodium levels due to the exchange of hardness ions like calcium and magnesium, can be detrimental to soil health and plant growth. Sodium can disrupt the balance of nutrients in the soil, and excessive sodium can lead to soil structure issues, which affects water infiltration and root development in plants.

In contrast, domestic hot water systems, cooling tower make-up water, and fixture supply lines often benefit from softened water as it helps prevent scale build-up and operational issues in appliances, plumbing, and systems due to hard minerals. By reducing hardness, these systems can operate more efficiently, prolonging their lifespan and ensuring optimal performance. Thus, the choice of not installing water softeners on lawn irrigation systems is primarily influenced by environmental considerations and the specific needs of plant and soil health.